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Starting in late August I'm getting frequent punctures, sometimes after only 30 km or so. They are always on the inside, and if the tube is patched, it appears that the patch "attracts" the puncture more than the rest of the tube; other than that, it does not appear that punctures happen on the same place, relative to the rim or the tyre. Several inspections did not reveal any sharp objects, or any issues with the rim or the tyre.

puncture through a patch

another puncture through a patch

Tyre rims leave clearly visible marks on patches and the punctures are between them in one case and on or near them in the other case. Is something wrong with the tyre? I changed it sometime in June and was using it without problems over most of the summer.

Update: this is how such puncture looks on a pristine tube:

puncture on a pristine tube

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  • What does your rim tape look like, down inside the valley of the rim ? "always on the inside" is telling.
    – Criggie ♦
    Commented Sep 7, 2023 at 10:17
  • Welcome to the site - thank you for asking a clear and well-illustrated question.
    – Criggie ♦
    Commented Sep 7, 2023 at 10:18
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    The tape looks intact, as far as I can tell - no bulges or tears.
    – volferine
    Commented Sep 7, 2023 at 10:49
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    @Criggie You might be right after all, according to a serviceman such punctures happen when the tape is a bit loose even though visually fine, folds when the tube is changed, and the tape edge cuts the tube. At least the last image is perfectly consistent with that. I was suggested to replace the tape and as a safety measure put an adhesive tape over it. I'll do that and update after a couple of rides.
    – volferine
    Commented Sep 8, 2023 at 11:49
  • Some 200 km later without accidents, looks like the problem - with some knocking on wood - has been solved. What now, @Criggie are you willing to turn your comment to an answer? I would accept it.
    – volferine
    Commented Sep 15, 2023 at 18:28

3 Answers 3

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Put the tube other way around so that there is a non-patched section at the suspect location. Does the tube still puncture from the same location?

If you get a puncture in the patched section, then the tube is gone. Get a new tube.

If you get a puncture in the same rim section, then the problem is in the rim. The location of the fresh puncture now gives the exact location of the problem in the rim. If you can't pinpoint anything wrong in the rim, rim tape (or strip), take a photo of the rim on the location where the punctures happen and add it to the question.

In general, the rim and the inside of the tyre should be smooth and should not leave any marks on the inner tube.

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  • "the tyre ... should not leave any marks" - it does; the tyre has fine "notches" on its edge, they leave barely visible marks on the tube and clearly visible marks on the softer part of tube patches. Is that a problem, or even the problem?
    – volferine
    Commented Sep 7, 2023 at 10:58
  • @volferine I have not personally encountered tyres like that... But it is fairly clear that the tyre marks probably are not the problem as the puncture is in the middle of the tube. One thing that comes to mind, have you checked the tyre bead that there isn't anything sharp protruding? I once had a strand of the bead wire poke out of the tyre causing a puncture.
    – Torben
    Commented Sep 8, 2023 at 9:07
  • I don't think this is the case, the punctures are not always on the same place (except when the tube was already patched) and I usually keep the tyre where it was when changing the tube; and yes, I inspected both the tyre and the rim quite carefully after last few incidents.
    – volferine
    Commented Sep 8, 2023 at 11:44
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I was getting mysterious flats for a long time until I decided to replace the tire, not the tube. I do not know how and why it was, the tire looked fully OK when inspecting. The damaged part looked like a very short and subtle dash that only leaks when the tube is sufficiently inflated.

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  • I think it might have solved my problem too if I was lucky when picking the new tyre - I suspect the tyre I bought in June was somehow more prone to roll the rim tape under it. But new rim tape is both cheaper and actually solves the actual problem.
    – volferine
    Commented Sep 16, 2023 at 12:33
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The most probable cause was the rim tape. Even though it was visually fine, it was already too loose and tended to fold, especially when I was replacing the tube or the tyre; and the edge of the folded rim tape would cut the tube. Replacing the tape (and for better results, covering it with a carpet tape) seems to have fixed the problem.

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